12/18/20151 Computer Security Introduction

12/18/20152 Basic Components 1.Confidentiality: Concealment of information (prevent unauthorized disclosure of information). 2.Integrity: Trustworthiness of data/resources (prevent unauthorized modifications). Data integrity Origin integrity (authentication) 3.Availability: Ability to use information/resources. (prevent unauthorized withholding of information/resources).

12/18/20153 Basic Components Additionally: Authenticity, accountability, reliability, safety, dependability, survivability...

12/18/20154 Confidentiality Historically, security is closely linked to secrecy. Security involved a few organizations dealing mainly with classified data. However, nowadays security extends far beyond confidentiality. Confidentiality involves: privacy: protection of private data, secrecy: protection of organizational data.

12/18/20155 Integrity “Making sure that everything is as it is supposed to be.” For Computer Security this means: Preventing unauthorized writing or modifications.

12/18/20156 Availability For Computer Systems this means that: Services are accessible and useable (without undue Delay) whenever needed by an authorized entity. For this we need fault-tolerance. Faults may be accidental or malicious ( Byzantine ). Denial of Service attacks are an example of malicious attacks.

12/18/20157 Relationship between Confidentiality Integrity and Availability Integrity Confidentiality Secure Availability

12/18/20158 Other security requirements Reliability – deals with accidental damage, Safety – deals with the impact of system failure caused by the environment, Dependability – reliance can be justifiably placed on the system Survivability – deals with the recovery of the system after massive failure. Accountability -- actions affecting security must be traceable to the responsible party. For this, –Audit information must be kept and protected, –Access control is needed.

12/18/20159 Basic Components Threats – potential violations of security Attacks – violations Attackers – those who execute the violations

12/18/ Threats Disclosure or unauthorized access Deception or acceptance of falsified data Disruption or interruption or prevention Usurpation or unauthorized control

12/18/ More threats Snooping (unauthorized interception) Modification or alteration –Active wiretapping –Man-in-the-middle attacks Masquerading or spoofing Repudiation of origin Denial of receipt Delay Denial of Service

12/18/ Policy and Mechanisms 1.A security policy is a statement of what is / is not allowed. 2.A security mechanism is a method or tool that enforces a security policy.

12/18/ Assumptions of trust Let P be the set of all possible states of a system Q be the set of secure states A mechanism is secure if P ≤ Q A mechanism is precise if P = Q A mechanism is broad if there are states in P which are not in Q

12/18/ Assurance Trust cannot be quantified precisely. System specifications design and implementation can provide a basis for how much one can trust a system. This is called assurance.

12/18/ Goals of Computer Security Security is about protecting assets. This involves: Prevention Detection Reaction (recover/restore assets)

12/18/ Computer Security How to achieve Computer Security: 1.Security principles/concepts: explore general principles/concepts that can be used as a guide to design secure information processing systems. 2.Security mechanisms: explore some of the security mechanisms that can be used to secure information processing systems. 3.Physical/Organizational security: consider physical & organizational security measures (policies)

12/18/ Computer Security Even at this general level there is disagreement on the precise definitions of some of the required security aspects. References: Orange book – US Dept of Defense, Trusted Computer System Evaluation Criteria. ITSEC – European Trusted Computer System Product Criteria. CTCPEC – Canadian Trusted Computer System Product Criteria

12/18/ Fundamental Dilemma: Functionality or Assurance Security mechanisms need additional computational Security policies interfere with working patterns, and can be very inconvenient. Managing security requires additional effort and costs. Ideally there should be a tradeoff.

12/18/ Operational issues –Cost-benefit analysis Example: a database with salary info, which is used by a second system to print pay checks –Risk analysis Environmental dependence Time dependence Remote risk

12/18/ Laws and Customs Export controls Laws of multiple jurisdiction Human issues –Organizational problems (who is responsible for what) –People problems (outsiders/insiders)

12/18/ Tying it all together: how ????